So far, 91 people have died from the lethal H5N1 bird flu strain.
Two dead swans in northern Germany and two birds found dead in Austria appear to have been infected with the virus, health officials in both countries reported.
The German swans were found on the island of Ruegen and regional agriculture ministry spokeswoman Iris Uellendahl said a preliminary test showed it was H5N1.
Agriculture Minister Horst Seehofer was scheduled to hold a news conference later Tuesday.
Samples from the birds were being take to an EU laboratory in Britain for a definitive test, Uellendahl said. Poultry within 2 miles of where the dead swans were found would be tested, she said.
Earlier Tuesday, Seehofer ordered that all domestic birds be kept indoors starting next week, moving up the previously planned measure to prevent migrating fowl from possibly spreading the virus.
Seehofer ordered farmers to enclose all poultry and other domestic birds in barns or cages with roofs starting Feb. 20. Authorities determined there was a heightened risk following the discovery of H5N1 in , the first time the highly infectious strain had been detected in the 25-member EU.
H5N1 also has occurred in birds in Asia, and the Middle East.
Germany initially had planned to order all birds indoors for at least two months starting March 1.
In Iran, the deadly strain of bird flu has killed 135 wild swans on the Caspian Sea coast, the first such cases detected in the Islamic Republic, the government said Tuesday.
Iran's official Islamic Republic News Agency said laboratory tests confirmed the H5N1 strain killed the swans at two locations in the Anzali marshlands during the past two weeks.
Iran's Veterinary Organization said all meat provided under Health Ministry regulations in Iran were free from bird flu and not dangerous to humans, IRNA said.
Meanwhile, Russia announced plans to begin human tests of a potential bird flu vaccine in April, the country's chief epidemiologist said Tuesday. Also Tuesday, Albania and Macedonia banned poultry imports from Greece, Italy, Bulgaria and Slovenia, where the H5N1 bird flu strain was detected over the weekend, authorities said.